Machine vision systems attempt to identify physical properties of a three-dimensional scene from two-dimensional intensity data provided by image sensors. Pixel-based algorithms, in which a scalar or vector is returned at each picture element (as in edge detection and optical flow algorithms, for example) produce an output at every grid point. Analog CMOS VLSI circuits, which often include on-chip photoreceptor arrays, have been developed for implementing such pixel-based algorithms. However, there has been little attention paid to developing special-purpose, application specific integrated circuits that advance the art beyond the early vision algorithms.
An area or region distinguishable from the background of a scene by visual features, such as brightness, depth, texture, or motion, for example, is easily identified by a human observer as an object separate from the background. In a machine vision system, a functionally related routine is required for the task of determining whether a particular point (pixel) is inside or outside one or more visual contours in a detected image. Thus, there is a need for a method and apparatus for distinguishing between object and background in the two-dimensional intensity data provided by an image sensor of a machine vision system.